Multiple-Input Multiple-Output (MIMO) technology is a technology for improving efficiency of data transmission and reception using multiple transmit antennas and multiple receive antennas rather than using one transmit antenna and one receive antenna. If a single antenna is used, a receive entity receives data through a single antenna path. In contrast, if multiple antennas are used, the receive entity receives data through several paths, accordingly data transmission rate and throughput may be improved, and the coverage may be extended.
To increase multiplexing gain of the MIMO operation, an MIMO transmit entity may use channel state information (CSI) fed back by the MIMO receive entity. The receive entity may determine the CSI by performing channel measurement using a predetermined reference signal (RS) from the transmit entity.